Williamtown contamination reports spur call for more testing

Posted 15 August 2016

 Firefighting chemicals

Confirmation of secondary PFAS contamination in groundwater near Salt Ash has prompted a request for further testing surrounding Williamtown RAAF base.

Suspected carcinogenic PFAS (per- and poly-fluorinated alkyl substances) chemicals, present in fire fighting foams used during drills at the air base, were detected in soils and groundwater surrounding the base last year.

NSW Environment Protection Authority (EPA) Senior Technical Advisor Kyle Horner said the Environmental Site Assessment released by Defence last week contained data gaps that need to be filled.

“In certain areas, particularly along the drains between the RAAF base and Salt Ash for example, there are effectively no data points. Similarly, to the south of the base there are limited data points,” Horner said.

“In presenting their findings, [Defence] have erred on the side of not misrepresenting the available data. But by not sampling these areas it is possible that they have missed areas of contamination.

“Our immediate response was to write Defence outlining these data gaps and requesting additional testing be undertaken to get a fuller picture of the distribution of the chemicals, because it’s a huge area.”

Horner said the natural topography of the region might heighten the risk of secondary contamination due to the many water routes capable of transporting the chemicals away from the base.

“It is a very complex area. Groundwater is very shallow, the soils are very permeable and, in addition to that, there’s a very extensive drainage network, with many of the drains originating at or near the base,” he said.

“The assessment shows that groundwater may have transported some of these chemicals as far as 2km away from the base. Surface water, on the other hand, can also transport some of these chemicals, and is currently doing so, more than 7km from the base.

“This is where it gets particularly complicated: where chemicals are being transported in surface water, there is the potential for them to then enter the groundwater system at distance from the base.”

Horner said a secondary groundwater contamination plume located at Salt Ash, some 10km east of the RAAF base, proves the necessity of testing other sites for secondary contamination in the area.

“The Salt Ash plume demonstrates that surface water can be lost from the high-elevation drains into the local groundwater system anywhere along the length of the drains,” he said.

 “The potential for spread of these contaminants into areas where there is no information [yet collected] is very real.

“We simply don’t know enough to say where it will or will not happen. And so in those areas EPA would like to see much more information generated.”

Human health precautions within the investigation area have been expanded from avoiding the consumption of groundwater, eggs and fish raised in contaminated water, to also include vegetables and stock that have been watered by affected groundwater. 

Where followed, these precautions will minimise people’s exposure while further data is collected on water and produce.

“With PFAS chemicals, generally dermal contact is not a major exposure pathway. The big risk is where you would directly ingest them into your body,” Horner said.

“The potential of exposure is quite high in the area because so many people have direct access to groundwater and depended on it for a number of applications.

“The good news is that Hunter Water and the State Government are in the process of reticulating water to all the properties in the investigation area, so by mid-2017 the number of people having to rely on groundwater for potable use will decrease significantly.”

Reticulating water to residents in the area is a $3.5 million project, but a priority for local residents and government, said Hunter Water CEO Jeremy Bath.

“Hunter Water has fast-tracked the 12km watermain project to provide town water to those people living inside the Investigation Area, having been told this is a project of significance to the NSW Government,” he said.

“The NSW Government recognised the enormous impact the investigation and uncertainty have had on the community and therefore provided funding for Hunter Water to connect the residents, businesses and Salt Ash Public School to its system.

“I hope having access to town water residents sourced from Hunter Water’s network will provide some much-needed relief.”

Hunter Water has also embargoed three groundwater pumps inside the investigation zone in the Tomago Sandbeds, representing 2% of the utility’s total supply.